We've been using UltraVNC for several years now, but recently we're running in to an issue. I believe it started with version 1.0.9.6.1. When we try to connect to a VNC server we sometimes get an error after being prompted for password that says "Server running as application" and it fails to make the connection. Searching around about this error it seems to happen for various reasons. I'm not sure what's causing it in our case because I don't believe I've changed the configuration of VNC at all. It doesn't happen on every machine. Last week I had 1.0.9.6.1 running as a viewer trying to connect to a 1.0.8.2 server and it happened. Traditionally we've been able to mix and max versions like this and haven't had any problems. I then tried upgrading the server to 1.0.9.6.1, but that didn't seem to help.

On the server side it's definitely running as a service and NOT as an application. Even if it was running as a application I don't understand why an error message exists for that. Upon trying to the connection it appears to reset the service. You can see the icon in the system tray disappear and then reload which leads me to believe it's somehow crashing the service and then it recovers. I'm not sure how this happens though because it looks like the default recovery action for the service is "no action" in Windows. With that in mind maybe that's not really what's happening.

Any thoughts on this? Both server and client are running Windows 7. Most of our machines are running Windows 7 now so I'm not sure if it's happening on Windows XP at this point. I'm starting to wonder if it's a video driver issue on the client end. Is that possible?

For me this was fixed by changing to "New MS Logon" authentication. I have no idea why the old "require MS logon" option no longer works. It worked for a long time and I'm not sure what made it stop working. Thanks again for the help.

I had this same problem. I thought it was UltraVNC and reinstalled it a couple times. Still didn't work. I could get to the machine by IP, but not to the windows share by name. Kept getting the running as an application error. I checked the DNS server. Turned out that I had two entries on the DNS server with the same IP address. Deleted both of them, powered both machines down and back on and VNC worked fine.